The trabecular meshwork of the eye is a principal site of outflow resistance to the aqueous humor. A protein called myocilin has been linked genetically to some forms of glaucoma. We have studied the expression of this protein in trabecular meshwork slices as well as human trabecular meshwork cells grown in tissue culture. This protein has a molecular mass of around 57kDa. We have seen an increase in the mRNA levels in cultured cells treated with dexamethasone, heat, and oxidative stress. We have started using gene array techniques to determine other components that have altered expression levels under these experimental conditions. We have studied the effects of dexamethasone on a number of primary cultures from various individual donors and will be comparing them with organs cultured material. Because of the difficulty in obtaining primary human trabecular cells in culture, we have attempted to get a mouse cell line established. The mouse trabecular meshwork is similar to human and contains a collecting canal reminiscent of Schlemm's canal. We have been able to get a cloned line of mouse trabecular meshwork cells by using the "immorto" transgenic mouse. The animal carries a temperature sensitive large T-antigen from the SV-40 virus linked to a promoter activated by gamma interferon. By growing cells under permissive conditions, we are able to maintain an actively dividing population of cells. When switched to higher temperatures without interferon, the cells stop dividing and start to express certain proteins that are present in trabecular meshwork. One of these proteins is myocilin. The mouse myocilin protein is slightly smaller than the human one. Fortunately the antibodies that we produced using a peptide fragment from the human also cross-react with the mouse. These cells are currently being used to screen for promoters that are specific to the trabecular meshwork and that might be used to generate transgenic mice. Our first sets of transgenic animals using the green fluorescent protein as a marker have been produced and we are now studying the expression of this construct in various tissues. We are also starting to look at the effects of a prostaglandin derivative, latanoprost acid on the trabecular meshwork. This compound causes a reduction on intraocular pressure and is currently used as a medication for glaucoma. It is thought to work not on the trabecular meshwork but rather on the uvealscleral outflow pathway. The exact mechanism by which it works is not understood and its long term effect on the trabecular meshwork is unknown. We will be using gene array technology with particular reference to those pathways that influence extracellular matrix production and remodeling.